Launcher does not open
Restart Windows, download a fresh installer from this site and check whether Windows Security quarantined the unsigned beta. Do not disable protection globally.
- Confirm Windows 10/11 x64
- Run from a local drive, not a network share
- Review Windows Security protection history
- Reinstall per user
A version will not install
Open Activity and identify the last failed URL or file. Confirm the PC clock, free disk space and HTTPS access before retrying.
- Keep at least 2 GB free for a basic install
- Try a current release before a snapshot
- Use a new empty game directory
- Avoid interrupted VPN or proxy connections
Java or game process fails
Clear a custom Java path so automatic resolution can run. Start with 4096 MB RAM and a current release.
- Leave Java blank for automatic mode
- Set RAM below total physical memory
- Disable fullscreen for the first test
- Update the graphics driver from the hardware vendor
Protect existing worlds
Never open an important world in an older version or snapshot without a copy. Use a separate directory for experiments.